Abstract：
PRRX1-fused mesenchymal neoplasm is a recently identified, rare subcutaneous soft tissue neoplasm that is characterized by fusion of PRRX1 (exon 1) with NCOA1 (exon 13) in the majority of reported cases. Although initially considered to be fibroblastic, a possibility of neural or neuroectodermal differentiation has been suggested in a subset of cases. We report a 26-year-old female with a 4.0 cm painless mass located in the subcutis of the left thigh. Microscopically, the tumor was well-circumscribed and multinodular and was composed of relatively monomorphic ovoid to spindle cells arranged in loose fascicles, trabeculae, and cords within alternating myxoid and fibrous matrix, and vascularized stroma. Mitotic figures were scarce and necrosis was not observed. By immunohistochemistry, the neoplastic cells demonstrated focal co-expression of S100 protein and SOX10 and were negative for epithelial membrane antigen, smooth muscle actin, desmin, CD34, STAT6, HMB45, Melan-A, and MUC4. The expression of Rb1 was retained. Targeted RNA-sequencing identified a novel transcript fusion of PRRX1 (exon 1)::NCOA1 (exon 15), which was further confirmed by reverse transcription polymerase chain reaction and Sanger sequencing. The tumor was narrowly excised and no tumor recurrence or metastasis was identified after 13 months of follow-up. In summary, we report a new case of PRRX1-fused mesenchymal neoplasm, expanding the molecular genetic spectrum and providing further support for possible neural or neuroectodermal differentiation of this emerging soft tissue tumor entity.
摘要：
PRRX1融合间充质肿瘤是最近发现的一种，在大多数报道的病例中，以PRRX1（外显子1）与NCOA1（外显子13）融合为特征的罕见皮下软组织肿瘤。虽然最初被认为是成纤维细胞，在一个亚组病例中已经提出了神经或神经外胚层分化的可能性.我们报告了一名26岁的女性，其左大腿皮下组织有4.0厘米的无痛肿块。微观上,肿瘤界限清楚，多结节，由相对单形卵圆形的梭形细胞组成，排列在松散的束中，小梁,和交替的粘液样和纤维基质内的绳索，和血管化的基质。有丝分裂图很少，未观察到坏死。通过免疫组织化学，肿瘤细胞显示S100蛋白和SOX10的局灶性共表达，上皮膜抗原阴性，平滑肌肌动蛋白，desmin,CD34,STAT6,HMB45,Melan-A,MUC4Rb1的表达得以保留。靶向RNA测序鉴定了PRRX1（外显子1）：：NCOA1（外显子15），逆转录聚合酶链反应和Sanger测序进一步证实了这一点。经13个月随访，肿瘤被狭小切除，未发现肿瘤复发或转移。总之,我们报告了一例PRRX1融合的间充质肿瘤，扩大分子遗传谱，并为这种新兴的软组织肿瘤实体的可能的神经或神经外胚层分化提供进一步的支持。
